1. Field of the Invention
The invention relates to Basic Input Output System (BIOS) in computer systems, and in particular, to an automatic switching method of multiple BIOS system files in a computer system and device thereof.
2. Description of the Related Art
A BIOS (Basic Input Output System) or a ROM-BIOS (read-only memory basic input output system), is a firmware permanently programmed in a computer for a computer system initialization and operation. The BIOS could provide the lowest level and most direct hardware control for the computer. Specifically, basic input output system serves to provide system testing and initialization upon computer booting.
In the startup process of a computer system, Power On Self Test (POST) is initially performed to check if all components are present and functioning properly. After that, system initialization is performed, including reconstructing of broken vectors, setting registers, and performing initialization and tests on external devices. An important part of the startup process is the BIOS file, comprising primarily parameters for hardware devices. During a computer power-up, the parameters in the BIOS file are read out and compared with actual hardware devices. If the parameters in the BIOS file match with the actual hardware devices, the computer starts booting process of an operation system. Otherwise, the startup process of the computer system is stopped.
FIG. 1 is a block diagram of a computer system including BIOS file 18. As shown in FIG. 1, BIOS file 18 is stored in a stand-alone Electrically Erasable Programmable Read-Only Memory (EEPROM) chip 16. Typically, EEPROM chip 16 is welded on a main board and coupled to a south bridge chip 14. In a normal condition, BIOS file 18 stored in EEPROM chip 16 comprises parameters matching with the hardware devices of the computer. However, in some exceptional conditions, e.g., when the computer system is attacked by a Chernobyl (CIH) virus, the BIOS file 18 will be modified by the CIH virus, so the computer system can not initialized properly due to mismatch between the parameters and the computer hardware devices. For solving above-mentioned problem, numbers of security mechanisms for BIOS file are provided, such as write protection, CIH virus protection, to prevent BIOS file 18 from illegally modified, or allow the computer to power up normally with a backup BIOS file in the case of illegal modification.
However, if the storage media storing the BIOS file or the signal interconnection is not working, for example, EEPROM chip 16 is damaged, or the interconnecting wires between the EEPROM chip 16 and south bridge chip 14 are not working, during the startup process, the computer continually tries to read BIOS file 18 without carrying on the startup process, or issuing an error signal. Under this condition, despite the presence of a backup BIOS file in the computer system, the computer cannot switch automatically to the backup BIOS file to read information and will remain disabled.
Thus it is crucial for a computer system with multiple BIOS files to be able to switch automatically to another BIOS file, when the storage media storing the present BIOS files is damaged.